The invention relates to a method for the computer-assisted visualization of a three-dimensional anatomical object, wherein at least two diagnostic image data records of the object are recorded and processed.
The invention furthermore relates to a diagnostic imaging device for carrying out the method and to a computer program for such a diagnostic imaging device.
In the field of angiography, two-dimensional X-ray projection methods are routinely used nowadays to show blood vessels by injecting suitable contrast agents. More recently, however, three-dimensional angiographic imaging methods are becoming increasingly important, such as three-dimensional X-ray imaging (CT) or magnetic resonance imaging (MR). The volume image data obtained by such methods contain interesting morphological information for diagnosing vascular disorders, such as stenoses or aneurysms for example. The visualization of the recorded vascular structures is important in both two-dimensional and three-dimensional medical imaging methods so that a treating physician can rapidly and reliably detect potential sources of risk (e.g. risk of infarct, thrombosis, or a risk that an aneurysm will burst).
Modern computer-assisted visualization methods make it possible on the one hand to show the course of blood vessels with high accuracy, wherein it may be possible to screen out any anatomical structures that do not belong to the vascular system of interest. Moreover, computer-assisted visualization methods are also a useful aid when planning interventions, such as percutaneous transluminal coronary angioplasty (PTCA) for example.
Furthermore, two- and three-dimensional imaging methods are known which are used not so much to clarify the morphology of blood vessels, as in the case of the above-described angiography methods, but rather make it possible to examine the function of an organ, for example the heart, which is supplied by the corresponding blood vessels. Such methods may be used in addition to angiographic methods to diagnose for example coronary vessel disorders. Methods are known in which temporal series of two- or three-dimensional diagnostic image data records of the heart are recorded and evaluated in order to discover functional disorders of the myocardium. For this purpose, regions of the myocardium which differ from the normal function are identified in the recorded image data. This may be assessed for example on the basis of thickened or thinned areas of the heart wall or even on the basis of observed abnormal movements of the heart wall. Moreover, functional imaging methods are known, such as the so-called MR perfusion method for example, which allow the blood flow through the myocardium to be examined. In the MR perfusion method, a parameter image is generated on the basis of a temporal sequence of MR images, wherein it is calculated, for each pixel, how the concentration of an applied contrast agent changes over time at the position of the respective pixel.
In order to allow simple and reliable diagnosis, it is desirable when visualizing diagnostic image data to combine morphological (e.g. angiographic) image data with functional image data in a joint representation, specifically such that pathological changes in morphology can be directly placed in relation with corresponding functional disturbances. Thus, a representation is to be possible for example which can be used by the treating physician to assign a stenosis that can be detected in an angiographic image to incorrect function in a corresponding region of the myocardium. For this purpose, in U.S. Pat. No. 5,151,856 it is proposed, starting from three-dimensional diagnostic image data records recorded by means of MR or CT, firstly to calculate a three-dimensional model of the examined myocardium using a computer. Based on this model, the functions in the various regions of the myocardium are then examined. In addition, two-dimensional angiographic projection images are recorded which show a two-dimensional representation of the morphology of the coronary arteries. Finally, the calculated model of the myocardium is visualized as a three-dimensional representation, wherein the recorded angiogram is superposed on this representation. To do this, the angiogram is suitably scaled and aligned in order to show the anatomical conditions in a manner that is as close to reality as possible. Regions of the myocardium in which functional disturbances have been identified can be emphasized using color according to the previously known method. The known method thus makes it possible to directly assign functional disturbances of the heart to visible morphological changes in the coronary arteries.
One particular disadvantage of the previously known method is that the superposition of the two-dimensional angiogram and the three-dimensional view of the heart model is not very well defined in geometric terms, and this leads to inaccuracies and errors which have a negative effect on diagnosis. Another disadvantage is that the three-dimensional view of the heart model, which in the previously known method is generated by a so-called rendering algorithm known per se, is not optimal for allowing standardized depiction, e.g. in medical reports. Moreover, the reproducibility of the three-dimensional visualization is not always satisfactory since the concrete representation depends on a large number of individually adaptable parameters. For these reasons, the doctors involved find such three-dimensional views rather undesirable.